; (function (window) {
    // 计算的构造函数
    function Computed() {

    }
    // 计算的方法
    Computed.prototype = {
        add: function (a, b) {
            return a + b;
        },
        subtract: function (a, b) {
            return a - b;
        },
        multiply: function (a, b) {
            return a * b
        },
        divide: function (a, b) {
            return a / b
        }
    }
    window.Computed = Computed;
})(window);